1. Field of the Invention
This invention relates to a flow measuring device according to the principle of the Karman vortex path.
2. Description of the Prior Art
Devices for measuring flow are known. For example, U.S. Pat. No. 3,972,232 describes and claims such a device in body is constructed of a T-shaped structure having a relatively narrow prismatic forward part of trapezoidal cross section and a following parallelepiped-shaped part of relatively large thickness. The means for measuring the pressure variations are arranged in the form a piezoelectric pickups and are positioned in the parallelepiped-shaped part in such a manner that the pressure-sensitive surfaces are attached to the upper and lower side surfaces of the parallelepiped-shaped part and are parallel to the flow.
In the phase of the vortices along the choke body of the known device are considered, one of skill in the art would not expect the periodic motion along the choke body to be in phase. It is also known in the art that the viscosity of any flowing fluid does insure that only extremely small phase shifts occur between adjacent vortex elements through a take-along effect when a short choke body is employed. However, where a longer choke body is employed, appreciable phase shifts can occur. These phase shifts cause an equalization of fluid flow parallel to the axis of the choke body which can lead to disturbances of the periodic vortex separation, which, in turn, can lead to a fading out or even a temporary disappearance of the vortex effects. All of these factors result in erroneous measurements.
It is therefore an object of this invention to provide a flow measuring device which provides accurate measurements.
It is also an object of this invention to provide a flowing measuring device which has a choke body in which phase equality of the vortex separation over the entire length of the choke body is assured.
It is still another object of this invention to provide a flow measuring device in which the means for measuring the periodic pressure fluctuation can be positioned anywhere on the choke body without a loss of accuracy in measurements.
Still other objects and advantages of the present invention will be obvious and apparent to those of skill in the art from the specification and the appended claims.